Field of the Invention
The present disclosure relates to inks, ink stored containers, inkjet recording apparatuses, and recorded matters.
Description of the Related Art
Inkjet printers have become remarkably widespread because of advantages such as low noise and low running costs. Color printers capable of performing printing over plain paper have also become a fixture in the market. However, it is very difficult to satisfy all properties needed, such as color reproducibility on an image, scratch resistance, durability, light resistance, driability of an image, character bleeding (feathering), color boundary bleeding (color bleeding), both-side printability, and discharging stability. Therefore, inks to be used are selected based on properties prioritized depending on the purposes.
Copper phthalocyanine pigments are widely used in cyan inks and characterized by an excellent chromogenic property and an excellent light resistance. However, the copper phthalocyanine pigments cannot compete with dyes in a chromogenic property and glossiness, and are particularly problematic in that as the amount of the pigment attached is increased to increase the image density, the color reproduced shifts to a bluish hue and cannot satisfy the cyan hue (L*: 53.9, a*: −37.5, and b*: −50.4) of the standard color (Japan color ver. 2).
As plotted in FIG. 1, the copper phthalocyanine pigments are weakly absorptive in a wavelength range of from 650 nm through 700 nm. Therefore, the color reproduced slightly wears a bluish hue because of insufficient absorption of red light (in a wavelength range of from 620 nm through 750 nm). Hence, if the copper phthalocyanine pigments are able to absorb light in this range more strongly, the color reproduced shifts to a greenish hue and can reproduce the standard color. However, if the light absorption in this range becomes excessively strong, there occurs a problem that the color purity becomes poor to degrade the saturation.
For example, there is proposed an aqueous pigment dispersion in which dispersed particles containing a copper phthalocyanine pigment and an anionic group-containing uncrosslinked organic polymeric compound and dispersed in an aqueous medium have an average particle diameter of from 50 nm through 200 nm, wherein a ratio [(A)/(B)] of absorbance (A) of the aqueous pigment dispersion at a local maximum of absorption in a wavelength range of from 610 nm through 620 nm to absorbance (B) of the aqueous pigment dispersion at a local maximum of absorption in a wavelength range of from 700 nm through 710 nm is in a range of from 1.00 through 1.26 (see, e.g., Japanese Unexamined Patent Application Publication No. 2003-342491).
There is also proposed a water-based ink containing a copper phthalocyanine pigment, wherein a maximum absorbance X of the water-based ink at an absorption peak present in a relatively short wavelength range and a maximum absorbance Y of the water-based ink at an absorption peak present in a relatively long wavelength range satisfy a condition of 0.75≤Y/X≤0.88 (see, e.g., Japanese Unexamined Patent Application Publication No. 2007-238809).